Reciprocating tool with balanced dual air cylinders

ABSTRACT

A reciprocating tool with balanced dual air cylinders including a pair of opposed piston assemblies and attachments which continuously move in opposite directions. A reversing pilot valve assembly is provided which is actuated by a drive piston assembly to direct the flow of air to a main reversing valve assembly. The main reversing valve assembly directs the flow of air to the drive and idler dual cylinders for reciprocating tool operation purposes.

United States Patent 1191 Knapp 1 June 28, 1974 1 RECIPROCATING TOOL WITH BALANCED 2,069,122 1/1937 Weaver 91/330 3,220,318 11/1965 McGuire 137/625.66

DUAL AIR CYLINDERS Inventor: Wallace C. Knapp, 1007 Roxleigh Rd., Towson, Md. 21204 Filed: Dec. 11, 1972 Appl. No; 314,161

US. Cl 91/40, 91/189, 91/304, 91/330 Int. Cl. F0ll 15/00 Field of Search 91/35, 39, 40, 189,218, 91/304, 313, 314, 412, 330, 337, 286, 287; 60/97 SE; 137/625.66

References Cited UNITED STATES PATENTS 11/1898 Rhodes 91/40 Primary EraminerEdgar W. Geoghegan Assistant EraminerA. M. Zupcic Attorney, Agent, or Firm-Karl L. Spivak, Esq.

[57] ABSTRACT A reciprocating tool with balanced dual air cylinders including a pair of opposed piston assemblies and attachments which continuously move in opposite directions. A reversing pilot valve assembly is provided which is actuated by a drive piston assembly to direct the flow of air to a main reversing valve assembly. The main reversing valve assembly directs the flow of air to the drive and idler dual cylinders for reciprocating tool operation purposes.

13 Claims, 5 Drawing Figures 108 h f '02 50 46126 1 30 e l 62 7o 72 78 1 s, 5 g 1111 I v l/ l 142 2 3 :1; 1 "lg"; g 50 A PATENTEDauuzs 1914 SHiEI 2 0f 4 PATENTEDsunze m4 FIG. 4

FIG. 5

RECIPROCATING TOOL WITH BALANCED DUAL AIR CYLINDERS BACKGROUND OF THE INVENTION The present invention relates generally to the field of power tools, and more particularly, is directed to a power reciprocating tool with balanced dual air cylinders.

Pneumatically operated power tools are well known and many such tools function through the principle of reciprocating pistons which are operative within air cylinders. One exemplary such device is disclosed in US. Pat. No. 2,804,847 which describes a tool incorporating a single reversing valve which is actuated by a drivepiston assembly. While the previous device as set forth in the patent is generally satisfactory in use, it has the disadvantage of stalling at any time that the reversing valve plunger happens to stop in a middle position. Additionally, many prior art reciprocating types of tools suffer from a disadvantage of generating unbalanced reciprocating forces, which forces then require great manual effort to hold the tool steady when in use.

SUMMARY OF THE INVENTION I The present invention relates generally to the field of reciprocating power tools, and more particularly, is directed to a novel reciprocating tool with balanced dual air cylinders.

The present invention relates to a portable, pneumatically operated, power tool which includes dual air cylinders and piston assemblies which are respectively reciprocal therewithin. The piston assemblies continuously, simultaneously, reciprocate in opposite directions to thereby completely balance the axial forces, which are generated by the piston assemblies and which operate inwardly and outwardly with respect to the dual cylinders. Compression spring type shock absorbers are provided in conjunction with the piston assemblies and these shock absorbers, in conjunction with the balanced, opposed, reciprocating forces of the dual piston assemblies give such smoothness of operation and such minimal reactions at the handles that relatively little physical exertion is required on the part of the operator to control relatively large quantities of input power.

It is therefore an object of the present invention to provide an improved reciprocating tool with balanced dual air cylinders of the type set forth.

It is another object of the present invention to prov vide a novel reciprocating tool with balanced dual air cylinders which incorporates means to reciprocate piston assemblies in a manner to counterbalance the generated forces, whereby minimal reactions are applied at the handles.

It is a further object of the present invention to provide a novel reciprocating tool with balanced dual air cylinders which includes a pair of opposed drive piston assemblies, a reversing pilot valve assembly, a main reversing valve plunger assembly and a main reversing valve assembly whereby the respective drive piston assemblies will be operated in precise opposed synchronism to balance opposed reciprocating forces.

It is another object of the present invention to provide a power reciprocating tool with balanced dual air cylinders wherein a reversing pilot valve assembly is actuated by a drive piston assembly which in turn directs the flow of air to a main reversing valve assembly to direct the air to power cooperating drive and idler dual cylinders.

It is further object of the present invention to provide a novel power reciprocating tool with balanced dual air cylinders which includes means to prevent stalling and further includes means to provide smooth and flawless operation through all ranges of speed and power application.

It is a further object of the present invention to provide a reciprocating tool with balanced dual air cylinders that is rugged in construction, simple in design and trouble free when in use.

Other objects and a fuller understanding of the invention will be had by referring to the following description and claims of a preferred embodiment thereof, taken in conjunction with the accompanying drawings wherein like reference characters refer to similar parts throughout the several views and in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a power tool constructed in accordance with the present invention.

FIG. 2 is a diagrammatic representation of the functioning parts of the tool of FIG. 1, showing the position of parts with the plunger assemblies in a first position.

FIG. 3 is a diagrammatic representation of the functioning parts of FIG. 1, with the plunger assemblies reciprocated to a second position.

FIG. 4 is a diagrammatic bottom plan view, on reduced scale, of the power tool of FIG. 1.

FIG. 5 is an end elevational view of power tool of FIG. 1, partially broken away to expose details of internal construction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of my invention selected for illustration in the drawings, and are not intended to define or limit the scope of the invention.

Referring now to the drawings, I show in FIG. 1 a reciprocating power tool generally designated 10 which includes an upper frame 12. At the transverse ends of the frame 12 are located a pair of tool operating handles l4, 16 which are employed to be grasped by the right and left hands (not shown) of the operator to apply the tool to the surface (not shown) being treated. Suspended from the frame 12 is a longitudinally disposed drive cylinder 18 within which reciprocates the drive piston assembly 72 in a manner hereinafter more fully set forth. Similarly, an idler cylinder 20 is suspended from the frame 12 in longitudinal, spaced alignment with and in opposed relation to the drive cylinder 18. An idler piston assembly 76 reciprocates within the idler cylinder 20 in the manner hereinafter more fully discussed. A reversing pilot valve assembly 22 is disposed atone end of the drive cylinder 18 and is operatively connected with the main valve assembly 24 through suitable tubing connections. The main valve assembly is rigidly connected to the frame 12 in a secure, vibration proof manner.

As best seen in FIGS. 1 and 2, a first supply of compressed air is introduced to the reversing pilot valve assembly 22 through the pilot air inlet connection 26 in well known manner, such as by using threaded, pressure fittings 106, inlet tubing 108 and an adaptor connector 110. The air flows through open channels 28 in the pilot reversing valve assembly 22 and exits the pilot valve assembly through the outlet port 30. The air under pressure flows from the outlet port 30 through suitable connecting tubing 32 and is introduced into the main reversing valve assembly 24 through the air inlet port 34 to impress air pressure on the right side of the plunger 36 of the main reversing valve plunger assembly 25. The air pressure on the right side of the main reversing valve plunger 36 creates a force which acts to urge the plunger 36 and its attached piston rod 38 and a valve seat 40 to the left as indicated by the arrow 39. However, before the plunger assembly 25 can move to the left the air pressure on the left side of the main valve assembly must be relieved. In order to accomplish this, the air pressure on the left side of the main valve assembly is relieved by flowing to atmosphere through the main valve exit port 42. A connecting tubing 44 carries the exhaust air and introduces it to the pilot valve assembly 22 through the inlet port 46 by employing a suitable threaded fitting 47. The exhaust air flows from the inlet port 46 through open interior channels 48 which are provided in the pilot valve assembly 22 and exhaust to atmosphere through the plurality of holes 50 which are in communication with the open channels 48. It will be noted that when air is impressed on the right side of the main valve assembly 24 through function of the reversing valve assembly 22, the valve seat 40 is pushed to the left of the main air inlet port 52 to thereby admit air under pressure into the main valve assembly 24 to the left of the plunger 36. (See FIG. 2).

Compressed air from a compressed air supply system (not shown) enters the main air inlet port 52 through a speed control and shut-off valve 68 which may be any conventional air valve suitable to both meter and shutoff the inlet air supply. The main air supply flows through the inlet port 52 into the interior space 54 which is defined between the left side of the plunger 36 and the right side of the valve seat 40. The air thus introduced flows through the interior space 54 and exits the main valve assembly through the respective exit ports 56, 58 for function of the drive cylinder 18 and idler cylinder as hereinafter more fully set forth. Air from the exit port 56 flows through the tubing 60 and enters the drive cylinder 18 through the inlet port 62. Similarly, the main air exhaust from the exit port 58 flows through tubing 64 and enters'the idler cylinder 20 through the inlet port 66. It will be noted that the air pressure entering the drive cylinder 18 through the inlet port 62 will impinge upon the left side of the drive piston 70 and thereby act to move the drive piston assembly 72 to the right. The airpressure through the conduit 64 enters the inlet port 66 of the idler cylinder 20 to the right of the idler piston 74 and therefore acts to urge the idler piston assembly 76 toward the left.

However, it will be noted that prior to the movement of the respective drive piston 70 and idler piston 74, the air pressure on the respective opposite sides of the pistons must first be relieved. In this regard, the air pressure to the right of the drive piston 70 is relieved by flowing to atmosphere through the cylinder exit port 78, through the exhaust tubing 80 and into the main valve assembly inlet .port 82. The air flows through open channels 84 in the main valve assembly and exits to atmosphere through the plurality of holes 86. Similarly, exhaust air from the idler cylinder 20 is directed through the idler cylinder exit port 88, through the idler cylinder exhaust tubing and into the main valve assembly inlet port 92. The exhaust flows from the inlet port 92 through open channels 94 and exhausts the main valve assembly 24 through the communicating exit holes 86.

With the valve seat 40 positioned as shown in FIG. 2, the air pressure introduced through the inlet port 62 causes the drive piston assembly 72 and its affixed piston rod 112 to move to the right until the rod end collar 98 contacts the spring housing 100 which is then also urged to the right by the air pressure. The movement to the right of the spring housing 100 compresses the compression spring 102. The compression force of the spring 102 absorbs the kinetic energy of the moving parts of the drive piston assembly 72 for shock absorbing purposes. A second compression spring 104 is positioned to receive and absorb the kinetic energy of the moving parts of the idler piston assembly 76 which act through the idler piston assembly rod 114.

When the action of the collar 98 upon the spring housing 100 occurs, the spring housing 100 compresses the spring 102 and forces the pilot valve plunger 116 to the right to its right position 1 18. With the pilot valve plunger in its right position 118 (FIG. 3), all air flows as described'in the description of FIG. 2 take place on the opposite sides of the pilot valve assembly 22 and the main valve assembly 24 causing a complete reversal of events at end of each drive piston assembly stroke.

Referring now to FIG. 3, the sequence of events with the pilot valve plunger 116 in its right position 118 will be described. A supply of compressed air is introduced to the reversing pilot valve assembly 22 in the manner hereinbefore described. With the pilot valve plunger, 116 urged to its right position 118, the compressed air flows through the open channels 29 in the pilot reversing valve assembly 22 and exits the pilot valve assembly through the port 46, which in this instance, serves as an outlet port. The air flows through the connecting tubing 44 and is introduced into the main reversing valve assembly 24 through the port 42 to impress air pressure on the left side of the plunger 120 of the main reversing valve plunger assembly 25. It will be noted that the piston rod 38 interconnects the plunger 120, 36 and carries the valve seat 40 so that all parts function as a unit. The air pressure on the left side of the main reversing valve plunger 120 creates a force which acts to urge the plunger 120 and the attached piston rod 38 and the valve seat 40 to the right, as indicated by the arrow 122. Before the plunger assembly 25 can move to the right, the air pressure on the right side of the main valve assembly must be relieved. In order to accomplish this, the air pressure on the right side of the main valve assembly 24 is relieved by flowing to atmosphere through the port 34. The connecting tubing 32 carries the exhaust air and introduces it to the pilot valve assembly through the port 30 and the conventional threaded fitting 124. The exhaust air flows from the port 30 through interior open channels 126 which are provided in the pilot valve assembly and exhaust to atmosphere through the plurality of holes 128 which are in communication with the open channels 126. It will be noted that when air is impressed on the left side of the main valve assembly 24 through function of the reversing valve assembly 22, the valve seat 40 is pushed to the right of the main air inlet-port 52 to thereby admit air under pressure to the main valve assembly 24 to the right of the plunger 120 (See FIG. 3).

With the operating parts in the positions illustrated in FIG. 3, the main air supply flows through the inlet port 52 into the interior space 130 which is defined between the right side of the plunger 120 and the left side of the valve seat 40. The air thus introduced flows through the interior space 130 and exits the main valve assembly 24 through the ports 82, 92 for function of the drive cylinder l8 and idler cylinder 20. Air from the port 82 flows through the tubing 80 and enters the drive cylinder 18 through the port 78. Similarly, the main air flows from the port 92 through the tubing 90 and enters the idler cylinder through the port 88. It will be noted that the air pressure entering the drive cylinder 18 through the port 78 will impinge upon the right side of the drive piston 70 and thereby act to move the drive piston assembly 72 to the left. The air pressure through the conduit 90 enters the port 88 of the idler cylinder 20 to the left of the idler piston 74 and therefore acts to urge the idler piston assembly 76 to the right.

Before either the drive piston 70 and idler piston 74 can move, the air pressure on the respective opposite sides of the pistons must first be relieved. In this regard, the air pressure to the left of the drive piston 70 is relieved by flowing the atmosphere through the cylinder port 62, the tubing 60 and into the main valve assembly port 56. The air flows through open channels 136 in the main valve assembly and exits to atmosphere through the plurality of holes 134. Similarly, exhaust air from the idler cylinder 20 is directed through the idler cylinder port 66, through the tubing 64 and into the main valve assembly port 58. The exhaust flows from the port 58 through open channels 136 and exhausts the main valve assembly 24 through the communicating exit holes 134.

With the valve seat 40 positioned as shown in FIG. 3, the air pressure introduced through the port 78 causes the drive piston assembly 72 and its affixed piston rod 112 to move to the left thereby separating the rod end collar 98 from contacting the spring housing 100. The compression spring 102 is then freed to allow the pilot valve plunger 116 to move to its left position as illustrated in FIG. 2 to thereby position the parts to repeat the cycle of operation. The complete reversal of events at the end of each drive piston assembly stroke sets up the continuous reversing motions of both piston assemblies 72, 76 and the attachments thereto. Preferably, a right spring housing 140 is employed to compress the right compression spring 142 upon movement of the drive piston 70 to its left position. The compression spring 142 serves to bias the pilot valve plunger 116 to its left position 138 to thereby expose the open channels 28, 48. When the plunger 116 is urged to its right position 118 as in FIG. 3, the open channels 126, 29 are exposed for air direction purposes.

In order to use thepower tool 10, attaching pads 144, 146 are conventionally affixed to the respective ends of the piston rods 112, 1 14 such as by employing threaded nuts 148, 150. The pads may be in any convenient form to facilitate the connection of the attachment being used, such as sanding blocks, waxing pads, buffers, etc.

A hollow, longitudinal, unifying rod 152 extends between end caps 154, 156 connected to the outboard ends of the cylinders 18, 20 for tool steadying purposes. The tube 152 is downwardly cut to provide a bottom groove 166 through which a pair of downwardly depending guides 158, 160 project. It is contemplated that the attachments (not shown) will each be connected respectively to an attaching pad 144, 146 and a guide 158, 160. In this manner, as the piston rods 112, 114 are reciprocated to reciprocate the pads 144, 146, the guides 158, 160 will also reciprocate along the hollow tube 152 within the bottom groove 166. The tube 152, acting through the guides 158, 160 serves to steady the device, to prevent movement about the piston rods 112, 114 and to assure true axial movement of the pads 114, 146 and any tools which may be attached thereto.

Although I have described the present invention with reference to the particular embodiments herein set forth, it is understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction may be resorted to without departing from the spirit and scope of the invention. Thus, the scope of the invention should not be limited by the foregoing specification, but rather only by the scope of the claims appended hereto.

I claim:

1. In a reciprocating tool, the combination of A. a frame;

B. a drive cylinder suspended from the frame,

1. said drive cylinder operatively carrying a drive piston assembly including a piston rod in reciprocating relationship,

2. said piston rod carrying a drive piston collar,

3. said drive piston assembly being reciprocal between a right position and a left position;

C. an idler cylinder suspended from the frame,

1. said idler cylinder operatively carrying an idler piston assembly in reciprocating relationship,

2. said idler piston assembly being reciprocal between a right position and a left position;

D. means to simultaneously reciprocate the drive piston assembly and the idler piston assembly in opposite directions;

E. a reversing pilot valve assembly disposed at one end of the drive cylinder,

1. the reversing pilot valve assembly including a pilot valve plunger,

2. the pilot valve plunger being movably responsive to the reciprocation of the drive piston assembly,

3. the reversing pilot valve assembly including left and right springs which bias the pilot valve plunger, one said spring being positioned at each end of the pilot valve plunger,

a. the said left and right springs being each retained within a respective right and left spring housing,

b. one spring housing is contacted and moved upon each reciprocation of the drive piston assembly by the drive piston collar to urge the pilot valve plunger between a first position and a second position,

F. a main valve assembly being interconnected between the drive cylinder, the idler cylinder and the reversing pilot valve assembly,

1. said main valve assembly including reversing plunger means which are responsive to the operation of the reversing pilot valve assembly to direct air alternately through a right path and a left path to both the drive cylinder and the idler cylinder,

2. the air from the right path and the left path generating forces to cause respective reciprocation of the said drive piston assembly and the said idler piston assembly.

2. The invention of claim 1 wherein the reversing plunger means of the main valve assembly includes a valve seat and a right plunger and a left plunger interconnected by a piston rod, the said valve seat being carried upon the piston rod and being reciprocal between a right position and a left position by function of the pilot valve plunger.

3. The invention of claim 2 wherein the main valve assembly is provided with an open interior space between the right and left plungers and a main air inlet port introducing an air supply into the interior space and wherein the valve seat controls the flow of air into the interior space.

4. The invention of claim 3 wherein the valve seat is moved to the right of the air inlet port when in its said right position to define a left air channel in the main valve assembly between the valve seat and the left plunger and wherein the valve seat is moved to the left of the air inlet port when in its said left position to define a right air channel in the main valve assembly between the valve seat and the right plunger.

5. The invention of claim 4 and left tubing interconnecting the left air channel to the left side of the idler piston assembly and to the right side of the drive piston assembly to simultaneously function the idler piston assembly and drive piston assembly in opposite directions.

6. The invention of claim 5 and right tubing interconnecting the right air channel to the right side of the idler piston assembly and to the left side of the drive piston assembly to simultaneously function the idler piston assembly and drive piston assembly in opposite directions.

7. The invention of claim 6 wherein a tool attaching pad is affixed to one end of the idler piston assembly and to one end of the drive piston assembly, said tool attaching pads being simultaneously reciprocated in opposite directions when the respective piston assemblies are reciprocated. I

8. The invention of claim 7 and guide rod carried by the frame and disposed in longitudinal spaced relationship to the drive cylinder and the idler cylinder.

9. The invention of claim 8 wherein the guide rod is fabricated to a generally hollow, elongate configuration and is provided with an elongate, bottom positioned groove.

10. The invention of claim 9 wherein a pair of guides are associated with the rod and are movable with respect thereto along the said bottom groove, an exterior portion of the guides extending exteriorly of rod.

1 1. The invention of claim 10 and means to interconnect a tool between each said tool attaching pad and one of the said guides to steady the tool as it is reciprocated upon operation of the device.

12. The invention of claim 1 wherein the spring housings have axial motion relative to the associated drive cylinder.

13. The invention of claim 12 wherein the other spring housing is contacted and moved upon each reciprocation of the drive piston assembly by a portion of the drive piston assembly to urge the pilot valve plunger from the second position to the first position. 

1. In a reciprocating tool, the combination of A. a frame; B. a drive cylinder suspended from the frame,
 1. said drive cylinder operatively carrying a drive piston assembly including a piston rod in reciprocating relationship,
 2. said piston rod carrying a drive piston collar,
 3. said drive piston assembly being reciprocal between a right position and a left position; C. an idler cylinder suspended from the frame,
 1. said idler cylinder operatively carrying an idler piston assembly in reciprocating relationship,
 2. said idler piston assembly being reciprocal between a rigHt position and a left position; D. means to simultaneously reciprocate the drive piston assembly and the idler piston assembly in opposite directions; E. a reversing pilot valve assembly disposed at one end of the drive cylinder,
 1. the reversing pilot valve assembly including a pilot valve plunger,
 2. the pilot valve plunger being movably responsive to the reciprocation of the drive piston assembly,
 3. the reversing pilot valve assembly including left and right springs which bias the pilot valve plunger, one said spring being positioned at each end of the pilot valve plunger, a. the said left and right springs being each retained within a respective right and left spring housing, b. one spring housing is contacted and moved upon each reciprocation of the drive piston assembly by the drive piston collar to urge the pilot valve plunger between a first position and a second position, F. a main valve assembly being interconnected between the drive cylinder, the idler cylinder and the reversing pilot valve assembly,
 1. said main valve assembly including reversing plunger means which are responsive to the operation of the reversing pilot valve assembly to direct air alternately through a right path and a left path to both the drive cylinder and the idler cylinder,
 2. the air from the right path and the left path generating forces to cause respective reciprocation of the said drive piston assembly and the said idler piston assembly.
 2. said piston rod carrying a drive piston collar,
 2. said idler piston assembly being reciprocal between a rigHt position and a left position; D. means to simultaneously reciprocate the drive piston assembly and the idler piston assembly in opposite directions; E. a reversing pilot valve assembly disposed at one end of the drive cylinder,
 2. the pilot valve plunger being movably responsive to the reciprocation of the drive piston assembly,
 2. the air from the right path and the left path generating forces to cause respective reciprocation of the said drive piston assembly and the said idler piston assembly.
 2. The invention of claim 1 wherein the reversing plunger means of the main valve assembly includes a valve seat and a right plunger and a left plunger interconnected by a piston rod, the said valve seat being carried upon the piston rod and being reciprocal between a right position and a left position by function of the pilot valve plunger.
 3. The invention of claim 2 wherein the main valve assembly is provided with an open interior space between the right and left plungers and a main air inlet port introducing an air supply into the interior space and wherein the valve seat controls the flow of air into the interior space.
 3. the reversing pilot valve assembly including left and right springs which bias the pilot valve plunger, one said spring being positioned at each end of the pilot valve plunger, a. the said left and right springs being each retained within a respective right and left spring housing, b. one spring housing is contacted and moved upon each reciprocation of the drive piston assembly by the drive piston collar to urge the pilot valve plunger between a first position and a second position, F. a main valve assembly being interconnected between the drive cylinder, the idler cylinder and the reversing pilot valve assembly,
 3. said drive piston assembly being reciprocal between a right position and a left position; C. an idler cylinder suspended from the frame,
 4. The invention of claim 3 wherein the valve seat is moved to the right of the air inlet port when in its said right position to define a left air channel in the main valve assembly between the valve seat and the left plunger and wherein the valve seat is moved to the left of the air inlet port when in its said left position to define a right air channel in the main valve assembly between the valve seat and the right plunger.
 5. The invention of claim 4 and left tubing interconnecting the left air channel to the left side of the idler piston assembly and to the right side of the drive piston assembly to simultaneously function the idler piston assembly and drive piston assembly in opposite directions.
 6. The invention of claim 5 and right tubing interconnecting the right air channel to the right side of the idler piston assembly and to the left side of the drive piston assembly to simultaneously function the idler piston assembly and drive piston assembly in opposite directions.
 7. The invention of claim 6 wherein a tool attaching pad is affixed to one end of the idler piston assembly and to one end of the drive piston assembly, said tool attaching pads being simultaneously reciprocated in opposite directions when the respective piston assemblies are reciprocated.
 8. The invention of claim 7 and guide rod carried by the frame and disposed in longitudinal spaced relationship to the drive cylinder and the idler cylinder.
 9. The invention of claim 8 wherein the guide rod is fabricated to a generally hollow, elongate configuration and is provided with an elongate, bottom positioned groove.
 10. The invention of claim 9 wherein a pair of guides are associated with the rod and are movable with respect thereto along the said bottom groove, an exterior portion of the guides extending exteriorly of rod.
 11. The invention of cLaim 10 and means to interconnect a tool between each said tool attaching pad and one of the said guides to steady the tool as it is reciprocated upon operation of the device.
 12. The invention of claim 1 wherein the spring housings have axial motion relative to the associated drive cylinder.
 13. The invention of claim 12 wherein the other spring housing is contacted and moved upon each reciprocation of the drive piston assembly by a portion of the drive piston assembly to urge the pilot valve plunger from the second position to the first position. 